1. Field of the Invention
The invention relates to automotive engine ignition diagnostics, and specifically to pickup probe devices for detecting characteristic engine output signals for display and analysis on suitable diagnostic equipment. The invention has particular application to non-intrusive pickup probe devices which do not require physical connection to the engine being analyzed.
2. Description of the Prior Art
Diagnostic systems for automotive engines are well known. Such systems typically have a display device, such as an oscilloscope, and a plurality of probe elements adapted to be coupled or connected to various components of the engine being analyzed for detecting a variety of engine output signals to analyze different engine operating conditions. Many of the conditions diagnosed by such systems relate to the ignition system of the automobile engine, and require access to the wires leading to the spark plugs, ignition coil, distributor and the like.
But recently new electronic engine ignitions have been used by automotive manufacturers. These systems include Distributorless Ignition Systems (DIS) wherein spark plugs are paired and fired simultaneously, and Direct Ignition (DI) wherein each spark plug has its own ignition coil. These systems facilitate complex computer control of engine function and do not require use of a distributor. Present oscilloscope diagnostics are not usable on these systems, at least in part because of inaccessibility of key portions of the ignition systems. For example, in such systems, the ignition coils are typically disposed beneath a shroud or cowl, so that there is no ready access to the primary and/or secondary wires of the ignition coils. Accordingly, current diagnostic systems which require direct connection or other coupling to the wires of the ignition coil cannot readily be used with the new types of electronic ignition systems.
In our copending U.S. application Ser. No. 404,518, filed Sept. 8, 1989, entitled "Magnetic Field Pickup for Automotive Engine Diagnostics" we disclose a hand-held pickup probe incorporating a unique electromagnetic sensing coil which provides an effective non-intrusive magnetic field pickup probe useful with electronic ignition systems. However, that probe requires each individual ignition element, such as an ignition coil, under test to be separately tested by the technician who must manually reposition the probe for each such coil.